1. Wave Nature of Light

2. Diffraction Diffraction is the bending of a wave around a barrier or through an opening into the shadow region.

3. Diffraction The amount of diffraction depends on the size of the barrier or opening compared to the wavelength of the wave. Longer wavelengths exhibit more diffraction. –Owl hoots around trees –Water waves around small boats –Light waves diffract for very small openings – on the order of 1 wavelength

4. Diffraction Applet This applet shows the diffraction of waves by a narrow opening.applet The waves bend into the shadow region.

5. Breakwater Diffraction Water waves diffract around barriers which have constructed as breakwaters.

6. Small Island Diffraction

7. Huygens’ Principle According to Huygens’ principle, each of the two slits in Young’s experiment acts as a point source of light waves. Christiaan Huygens (1629-1695)

8. Ripple Tank Waves The crests of water waves act as converging lenses for the light shining from above. On the screen, the crests are bright, and the troughs are dark.

9. Ripple Tank Waves

11. Diffraction Slit Width Variation

12. Diffraction Pattern - Fingers Make a narrow opening between two fingers and look through the opening at a light. You will see thin fringes resembling hairs. These are nodes or dark fringes.

13. Diffraction – Slit Width

14. Razor Blade & Penny Diffraction

15. Poisson’s Spot Explained

16. Diffraction Links http://www.cfd-solutions.co.uk/waves.htm http://www.spacesciencegroup.nsula.edu/les sons/defaultie.asp?Theme=waves&PageNa me=diffractionhttp://www.spacesciencegroup.nsula.edu/les sons/defaultie.asp?Theme=waves&PageNa me=diffraction http://lectureonline.cl.msu.edu/~mmp/kap13 /cd372.htmhttp://lectureonline.cl.msu.edu/~mmp/kap13 /cd372.htm http://www.glenbrook.k12.il.us/gbssci/phys/ Class/waves/u10l3b.htmlhttp://www.glenbrook.k12.il.us/gbssci/phys/ Class/waves/u10l3b.html http://www.coastal.udel.edu/ngs/waves.html

17. Interference When two waves interfere, the resulting displacement of the medium at any location is the algebraic sum of the displacements of the individual waves at that same location. This is called the principle of superposition. Constructive Interference Antinode Destructive Interference Node

18. Double Source Interference When 2 periodic circular patterns interfere, a pattern of constructive and destructive interference emerges. “Lines” connecting nodes are called nodal lines “Lines” connecting antinodes are called antinodal lines

19. Double Source Nodal Lines

20. Ripple Tank Waves The diffraction due to the two narrow openings results in a pattern of nodal and antinodal lines similar to that of a double source interference pattern.

21. Ripple Tank Waves A A A N N Antinodal Lines Nodal Lines

22. Inserting a Screen AAANNAN d

23. Double Source Interference When 2 periodic circular patterns interfere, a pattern of constructive and destructive interference emerges. “Lines” connecting nodes are called nodal lines “Lines” connecting antinodes are called antinodal lines

24. Double Source Applets

25. Thomas Young Scientist Physician Renaissance Man Interference Elastic Behavior of Solids Kinetic Energy Work and Energy Connection 1773 - 1829

26. Double Slit Interference

27. Light Interference Interference is most noticeable when light is: Monochromatic -- This means light with a specific wavelength. Coherent. This means the phase difference between the light waves remains constant over time. Laser light is monochromatic and coherent. Light from incandescent lamps is incoherent.

28. Coherent & Incoherent Light

29. Incoherent Light Atoms emit radiation. For example the "excited" neon atoms in a neon sign emit light. Normally, atoms radiate their light in random directions at random times. The result is incoherent light.

30. Young’s Double Slit Applets

31. Young’s Double Slit Layout

32. Wavelength Comparisons

33. Interference - Wavelength

34. Reflections at Boundaries Free End Reflection No phase change Slow Medium to Fast Medium to Slow Medium Fixed End Reflection 180 o phase change

35. Thin Film Interference

36. Phase change of ray 1 Phase change of ray 2 In terms of wavelength in vacuum

37. Thin Film Interference difference in phase shifts of the two rays. Destructive Interference Constructive Interference

38. Air Wedge Interference

40. Newton’s Rings

41. Air Wedge Interference Destructive InterferenceConstructive Interference Fringe Spacing

42. Iridescence

45. Soap Film Interference This soap film varies in thickness and produces a rainbow of colors. The top part is so thin it looks black. All colors destructively interfere there.

46. Sample 6 A soap bubble is illuminated by a combination of red light (λ = 692 nm) and blue light (λ = 519 nm). What minimum thickness of the soap bubble film will result in blue light being not reflected?

47. Parallax Apparent change in position of object due to shift in position of observer

48. Camera 1 – Camera 2

49. Binocular Vision Two Eyes Camera 1 – Camera 2 One of the reasons that we can perceive depth. –Our brain uses the two images (one from each eye) to judge the distance to an object. –Subconscious use of parallax

50. 3D Circle

51. Cow

52. Unpolarized & Polarized Light

53. Polarization of Light Unpolarized Polarized Electric fields of unpolarized light vibrate in all directions perpendicular to the direction the light travels. A polarizing filter can constrain light to vibrate in only one direction

54. Polarizing Filters

55. Polarization

57. Reflected Horizontally Polarized Polarization of Reflected Light

58. Polarizing Glasses Which pair of glasses is best suited for automobile drivers? (The polarization axes are shown by the straight lines.)

59. Two Polarizers Perpendicular Axes Parallel Axes

60. Insert Third Polarizer

61. Polarization Applets Molecular View of Polarization Polarization of Reflected Light Polarizing Filters

62. LASER Light Amplification by Stimulated Emission of Radiation

63. Stimulated Emission If a photon whose frequency corresponds to the energy difference between the excited and ground states strikes an excited atom, the atom is stimulated as it falls back to a lower energy state to emit a second photon of the same (or a proportional) frequency, in phase with and in the same direction as the bombarding photon. This process is called stimulated emission. The bombarding photon and the emitted photon may then each strike other excited atoms, stimulating further emission of photons, all of the same frequency and phase. This process produces a sudden burst of coherent radiation as all the atoms discharge in a rapid chain reaction.

64. Laser A laser is a device that creates and amplifies a narrow, intense beam of coherent light. In a ruby laser, light from the flash lamp, in what is called "optical pumping", excites the molecules in the ruby rod, and they bounce back and forth between two mirrors until coherent light escapes from the cavity.

65. Interference in CDs Laser shines light onto track of CD Discs have “pits” in the surface Sensor reads signal from laser CD Burners

66. Constructive Interference When entire beam reflects from the “pit” or when entire beam reflects from the “land” – constructive interference results – “on”

67. Destructive Interference “Pits” are ¼ above the “land” When part of beam reflects from “pit” and part from “land” Destructive interference – interpreted as “off”

68. Laser Scans Disc Intensity of the reflected light varies as the disc rotates. Intensity is measured and interpreted as a series of ones and zeros (digital information). Information is then relayed to other systems that interpret it.

69. Holography

70. Viewing a Hologram